Non-zero density QCD by the Taylor expansion method: The isentropic equation of state, hadronic fluctuations and more

TL;DR

This paper employs the Taylor expansion method to analyze non-zero baryon chemical potential in QCD, providing insights into the equation of state, hadronic fluctuations, and the convergence radius, thus advancing understanding of the QCD phase diagram.

Contribution

It presents new calculations of expansion coefficients up to sixth order using improved staggered fermions, and constructs the isentropic equation of state and fluctuations for the first time with this approach.

Findings

Expansion coefficients calculated up to sixth order.

Constructed the isentropic equation of state.

Estimated the radius of convergence of the expansion.

Abstract

We discuss the Taylor expansion approach to non-zero baryon chemical potential ($\mu_B$) and present results on expanion coefficients of the pressure and energy density up to the 6-th order in $\mu_B$. Calculations have been performed with (2+1)-flavor of improved staggerd fermions (p4fat3) and almost physical masses on lattices with temporal extent of four and six time slices. We use the expansion coefficients to construct the isentropic equation of state on lines of constant entropy per baryon number and various different hadronic fluctuations. Furthermore, we estimate the radius of convegence of our expansion, which can be seen as a method to analyze the structure of the QCD phase diagram.